292 NOTES AND MEMORANDA. 



tube, connected at the end with the green portion and by the other 

 opening into the bladder. 



The entire tubular gland is lined by a single layer of epithelial 

 cells, outside which is a fine structureless tunica propria, containing 

 strongly refracting nuclei. There is no cuticular lining to the tube, 

 which thus differs very markedly from the Malpighian vessels of insects. 

 In the yellow portion the cells are sharply defined and convex on their 

 inner surface. In the green part of the tube the cells are large, and 

 their protoplasm is in connection with a peculiar network of pseudo- 

 podial processes which extend into projections of the wall into the 

 lumen of the tube. In the proximal portion (that nearest to the green 

 section) of the white part of the tube the walls are smooth, and lined 

 by small cells approaching the pavement form. In its distal portion 

 mammilliform or dendritic processes of the wall project into the 

 cavity, often giving the tube a spongy appearance, and the cells have 

 long broad processes developed from their inner surfaces. The 

 epithelium of the bladder agrees with that of the smooth portion of 

 the tube. 



The products of secretion are seen in the white and green but not 

 in the yellow portion of the gland, as yellowish, rather highly 

 refracting drops on the surface of the cells. Probably the yellow 

 part secretes a substance soluble in alcobol. That part of the white 

 tube with tessclated epithelium most likely acts merely as a duct. 



The anterior portions of the gland and bladder are supplied by a 

 branch of the antennary arteries, their posterior portions by the 

 sternal arteries ; these break up into a rich network of capillaries in 

 all parts of the gland. The nerve supply of the bladder is also 

 derived from two sources, its first part being sujiplied by a branch of 

 antennary nerves (coming from the supra-oesophageal ganglion), its 

 hinder part by a nerve from the infra-oisophageal ganglion. No nerves 

 were observed in the gland itself. 



Action of the Heart of the Crayfish. — M. Felix Plateau, of 

 Ghent, has succeeded in applying the graphic method to the study of 

 the heart's action in the crayfish. A curve is obtained, of which the 

 ascending portions correspond to diastole, and the descending to 

 systole, contrary to what obtains in the Vertebrate heart. It is 

 strikingly like the trace of the contraction of a muscle ; a rapid, 

 almost sudden ascent, with a short flat summit, then a gradual de- 

 scent, at first quicker, then slower. This, however, does not represent 

 the whole truth ; it is possible also to demonstrate a wave affecting 

 the muscular wall of the heart, and travelling from behind forwards, 

 thus demonstrating that this condensed heart is a true dorsal vessel. 

 On the stimulus of the entrance of renovated blood, it is only the 

 hinder half or two-thirds of the heart that contracts immediately. 

 This forces blood into the forward half, which contracts only when 

 the posterior division is again dilating. When the temperature is 

 increased, as a general rule the diastolic jDhase is abbreviated, the 

 number of pulsations rising at the same time. M. Plateau has also 

 succeeded in making experiments on the action of the cardiac nerve 

 of Lemoine, an unpaired branch of the stomatogastric ganglion. It 



